It is known to apply automotive trim pieces to the exterior of wheeled vehicles such as cars and trucks. Examples of such trim include accent stripes, side door bumper elements, claddings, wheel covers, grills, and bumper fascia. The instant invention further applies to exterior vehicle components which have previously been made of plastic materials, such as door sides and the like.
In the prior art, exterior molded automotive trim components are typically painted in order to provide them with color. It is desirable that the paint color be compatible with the appearance of the vehicle (e.g. the same as that of the vehicle, or complimentary thereto). Following painting of a molded piece of trim, a clear coat is often sprayed over the paint to give it luster.
Prior to painting molded trim, it has often been necessary to prepare the exterior surfaces of such components by applying a primer which promotes adhesion of the paint to the surface of the molded component. After the paint is applied over the primer by spraying, the color appearance of the final product results from the pigmentation of the paint layer which is sandwiched between the sprayed-on clear coat and the underlying primer.
Unfortunately, spray painting of molded components for use on vehicles is often undesirable due to the potential for resulting paint lines, a need for masking tape, and the corresponding labor involved. Moreover, spray painting is undesirable due to the high capital equipment cost associated with paint line equipment, and potentially hazardous environmental issues relating to required solvents and the like. Thus, it will be apparent to those of skill in the art that it would be desirable if automotive trim components could be manufactured in a manner so that they were color compatible with automotive exteriors, without the need for spray painting the molded components.
It is also known to manufacture automotive exterior plastic components simply as a product in the condition which it comes out of the mold (i.e. without painting). For such components, the plastic which is used to injection mold the component may include color pigmentation so that the desired color appears not only on the surface but throughout the molded article. Unfortunately, the surface of such molded components, while initially presenting a desirable color, lacks luster and also can be easily scratched and/or marred to further detract from its lack of luster.
Molded automotive trim components have numerous requirements or desires known by automotive manufacturers. It is desirable that such trim components maintain their form without becoming too soft in hot weather conditions, or too brittle in cold weather. Such products should also be capable of holding up and withstanding exposure to ultraviolet (UV) rays of the sun. It is also desired that certain components be capable of a certain amount of flexibility without permanently deforming or denting. It is desirable that surface appearances of such components exhibit considerable luster.
Another approach to automotive trim coloring includes the use of dry paint film. A dry paint-coated laminate can be utilized to replace conventional spray paint. The dry laminate is made by applying a paint coat to a casting sheet by way of conventional paint coating techniques. The dried paint coat is then transferred from the casting sheet to a trim panel by way of known dry paint transfer technology. The laminate may later be thermo-formed into a three dimensional shape and then bonded or integrally molded to an underlying plastic car body member or panel. Such known dry paint film technology is disclosed, for example, in U.S. Pat. No. 5,725,712, the entire disclosure of which is incorporated herein by reference.
Prior art FIGS. 1-10 will be referred to for the purpose of describing conventional dry paint film technology for application to automotive trim components. FIG. 1 illustrates a conventional automobile, which includes numerous exterior plastic molded body components which may be colored. Automobile 1 in FIG. 1 includes bumper fascia 3, wheel covers 5, and many other exterior components which may be made via injection molding technology.
The '712 patent describes a system for coloring automotive trim components. The first step in this dry paint film approach is the provision of the dry laminate 7 of FIG. 2. Laminate 7 includes self-supporting carrier sheet 9 (i.e. casting film), clear coat 11, paint coat 13, and optional size coat 15 for providing adhesion to a backing sheet in a subsequent laminating step. In order to manufacture laminate 7, clear coat 11 is coated onto carrier 9 by a complicated reverse roll coating process shown in prior art FIG. 3, in which clear coat lacquer is contained in coating pan 17. Applicator roll 19 picks up lacquer from the pan and coats it onto carrier film 21 (or 9) after it passes over guide roll 23. After exiting the nip (or die) between applicator roll 19 and rubber backup roll 25, the coated carrier film 27 passes to a multiple zone drying oven. The laminate is dried in the oven at temperatures of from about 250.degree.-400.degree. F. via a multi-stage drying process. After drying, a two layered laminate, including carrier 9 and clear coat 11, is provided.
Color coat 13 is then bonded to clear coat 11 after the clear coat has dried on carrier 9. Color paint coat 13 is typically applied to the carrier by reverse roller coating techniques as shown in FIG. 3, with the color coat being dried by passing it through the multiple drying zones discussed above in curing the clear coat. Thus, the complicated reverse rolling techniques and multi-zone drying ovens of FIG. 3 must be utilized on numerous occasions in order to apply the clear coat and the color coat to the carrier.
Size coat 15 is next coated onto paint coat 13, and is typically applied as a thermoplastic and dried in the same multi-step drying step utilized above for the clear and color coats. The result is laminate 7 of FIG. 2.
Laminate 7 is next laminated to a thermo-formable backing sheet by dry paint transfer laminating techniques shown in FIG. 4, to form laminate 29 of FIG. 5. During this burdensome laminating step of FIG. 4, paint-coated laminate 7 is stored on unwind roll 31 and a flexible 20 mil thick ABS backing sheet 33 is stored on unwind roll 35. When rolls 31 and 35 unwind as shown in FIG. 4, and the webs respectively pass over drums 37, paint-coated laminate 7 and ABS sheet 33 are bonded together between heated laminating drum 39 and roll 41. Laminate 7 is bonded to sheet 33 as the two pass between rolls 39 and 41. The resulting laminate 29 then passes onto storage drum 43. The result is a roll of the laminate 29 of FIG. 5, including a color determined by the colored pigment in paint layer 13. Laminate 29 includes backing sheet 33, size coat 15, color coat 13, and clear coat 11.
Next, laminate 29 is thermo-formed into a desired three dimensional shape. Referring to FIG. 6, laminate 29 is placed inside clamping frame 45 of a vacuum-forming machine. Frame 45 is moved into oven 47 for heating laminate 29. Backing sheet 33 is heated in oven 47 and laminate 29 sags as shown at 49. Then, clamping frame 45 is moved back to the position above vacuum-forming buck 51. The preheated laminate 29 is next vacuum-formed into a desired three dimensional shape by drawing a vacuum on buck 51 through connection 53 to a vacuum pump, and buck 51 is raised to its FIG. 7 position. Vacuum is pulled through holes in buck 51 to force the pre-heated plastic of laminate 29 into the shape of the working surface of buck 51.
Next, the thermo-formed three dimensionally shaped laminate 29 is bonded to a substrate panel as shown in FIGS. 8-9. Laminate 29 is placed into an injection mold and fused to the face of an injection molded substrate 55. FIG. 8 shows preformed laminate 29 placed in the mold cavity between front and rear mold halves 57 and 59. The inside surface 61 of mold half 57 nearly identically matches the exterior contour of paint-coated laminate 29. Surface 61 may be a rigid, high gloss, highly polished surface which is substantially free of surface defects so that no or few defects are transferred to the high gloss, clear coated surface of the laminate. After laminate 29 is in place, semi-molten injection molding material 55 is injected into the mold through passage 63 behind pre-formed laminate 29. The molding material conforms to the shape of the mold cavity and is permanently fused to backing sheet 33 of laminate 29 in the mold. A cross-section of the resulting three-dimensionally molded trim component is shown in FIG. 10.
As can be seen above, dry paint film transfer technology is very burdensome and complicated. For example, the aforesaid process illustrated in FIGS. 1-10 requires going through rollers and dryers on numerous occasions, as well as the required length of time to do same. The process is very expensive due to the process requirements and materials. Moreover, it has been found that the life span of such trim components may be limited because they lose color quickly upon exposure to heat, sun, chemicals, and the like. The requirements for all of the rollers, drums, laminates, vacuum-forming dies and processes, and injection molding equipment is very expensive. The cost of tooling is very high due to the requirement of vacuum-form tooling, injection tooling, trim tooling, drums and rollers, and the like. Moreover, the trimming of materials after placement into the vacuum-forming and injection cavities results in much waste, and lower yields. Problems have also been experienced with regard to maintaining DOI (depth of image), in that DOI may be lost due to deep draws in the components. Depth of pockets or corners in the final molded components is also limited due to the dry paint film, as it may not be over-stretched or it will lose color and/or gloss.
U.S. Pat. No. 5,037,680, incorporated herein by reference, discloses an exterior automotive component with a pigmented substrate and a clear coating thereon. The substrate may be of a thermoplastic polyolefin. Unfortunately, the clear coating material in the '680 patent is deposited onto the substrate in liquid form, e.g. spraying, brushing, dipping, flow coating, etc. This spray or wet application is undesirable for the reasons set forth above (e.g. environmental concerns, need for solvents, expensive equipment required, etc.).
It is apparent from the above, that there exists a need in the art for colored and molded automotive trim components which: (i) may be manufactured without the requirement of prior art dry color paint film transfer; (ii) are colored so as to match or compliment a color of the surrounding vehicle; (iii) may be manufactured at a lesser cost than conventional dry paint film techniques; (iv) have an adequate life span upon exposure to heat, sun, chemicals, and the like; (v) may be manufactured without the requirement of needing to pass through chrome rollers and/or dryers on multiple occasions; (vi) may be manufactured without excessive capital expenditure; (vii) may be manufactured without wasting large amounts of trimmed off materials; (viii) maintain DOI; (ix) are scratch resistant, have luster, and are resistant to marring; (x) have high gloss and retention of same; (xi) have color uniformity; (xii) are resistant to gasoline and solvents, and acid spotting; (xiii) have satisfactory hardness and abrasion resistance; (xiv) have satisfactory impact strength; (xv) have acceptable UV resistance; (xvi) are resistant to water and humidity exposure; and/or may be manufactured without the need to "spray" on or otherwise apply a clear coat in liquid form. There exists a need in the art for molded trim products having any or all of the aforesaid characteristics, as well as methods of manufacturing the same.
It is a purpose of this invention to fulfill any and all of the above-described needs in the art, as well as other needs which will become apparent to the skilled artisan from the following detailed description of this invention.